Search

Developing low density and efficient dielectric loss materials has become a research hotspot, which can greatly meet the demands of modern radars and settle the problem of electromagnetic wave pollution. Herein, a series of N-doped ordered mesoporous carbon (OMC) materials with different nitrogen content were prepared via a modified self-assembly method and defect engineering in subsequent calcination treatment. It was discovered that the content and type of nitrogen doping can be effectively modulated by the amount of precursor dicyandiamide, resulting in the changes in porous structure, carbon defects, electromagnetic properties, microwave absorption (MA) performance and radar cross section (RCS) reduction values. Remarkably, as-fabricated OMC/N2.5 displays ideal MA performance, whose minimum reflection loss (RL(min)) value reaches −35.3 dB at 7.76 GHz (3.0 mm) and its effective absorption bandwidth reaches 3.52 GHz (10.64–14.16 GHz, 2.0 mm). Furthermore, the optimal RCS reduction values can be obtained as 12.01 dB·m2 when the detection theta is 30°, which validly reduces the chances of being detected by radar. Thus, this work opens up a novel way for the development of lightweight and high-efficiency MA materials.

As a vital parameter in living cells and tissues, the micro-environment is crucial for the living organisms. Significantly, organelles require proper micro-environment to achieve normal physiological processes, and the micro-environment in organelles can reflect the state of organelles in living cells. Moreover, some abnormal micro-environments in organelles are closely related to organelle dysfunction and disease development. So, visualizing and monitoring the variation of micro-environments in organelles is helpful for physiologists and pathologists to study the mechanisms of the relative diseases. Recently, a large variety of fluorescent probes was developed to study the micro-environments in living cells and tissues. However, the systematic and comprehensive reviews on the organelle micro-environment in living cells and tissues have rarely been published, which may hinder the research progress in the field of organic fluorescent probes. In this review, we will summarize the organic fluorescent probes for monitoring the microenvironment, such as viscosity, pH values, polarity, and temperature. Further, diverse organelles (mitochondria, lysosome, endoplasmic reticulum, cell membrane) about microenvironments will be displayed. In this process, the fluorescent probes about the “off-on” and ratiometric category (the diverse fluorescence emission) will be discussed. Moreover, the molecular designing, chemical synthesis, fluorescent mechanism, and the bio-applications of these organic fluorescent probes in cells and tissues will also be discussed. Significantly, the merits and defects of current microenvironment-sensitive probes are outlined and discussed, and the development tendency and challenges for this kind of probe are presented. In brief, this review mainly summarizes some typical examples and highlights the progress of organic fluorescent probes for monitoring micro-environments in living cells and tissues in recent research. We anticipate that this review will deepen the understanding of microenvironment in cells and tissues and facilitate the studies and development of physiology and pathology.

Abstract Perovskite solar cells are used in silicon-based tandem solar cells due to their tunable band gap, high absorption coefficient and low preparation cost. However, the relatively large optical refractive index of bottom silicon, in comparison with that of top perovskite absorber layers, results in significant reflection losses in two-terminal devices. Therefore, light management is crucial to improve photocurrent absorption in the Si bottom cell. In this paper, nanoholes array filled with TiO2 is introduced into bottom cells design. By finite-difference time-domain methods, the absorption efficiency and photocurrent density in the range of 300–1100 nm has been analyzed, and the structural parameters have been also optimized. Our calculations show the photocurrent density which tends to be saturated with the increase in the height of the nanoholes. The absorption enhancement modes of photons at different wavelengths have been analyzed intuitively by the distribution of electric field. These results enable a viable and convenient route toward high efficiency design of perovskite/Si tandem solar cells.

Gallium sulfide (GaS) is a layered metal monochalcogenide semiconductor that has recently garnered considerable attention in various fields. In this study, we investigated the nonlinear absorption characteristics of multilayer β-GaS thin films on sapphire substrate by using femtosecond open-aperture Z-scan method. The β-GaS films exhibit saturable absorption behavior at 532 nm while nonlinear absorption appears under 650 nm excitation. The nonlinear absorption coefficient of β-GaS was determined to be −1.8 × 10–8 m/W and 4.9 × 10–8 m/W at 532 and 650 nm, respectively. The carrier dynamics of β-GaS films was studied via femtosecond transient absorption (TA) measurements. The TA results demonstrated that β-GaS films have broad photo-induced absorption in the visible regime and sub-nanosecond lifetime. Our results indicate that gallium sulfide has large nonlinear optical response and long carrier lifetime, which could be applied in future photonic devices.

Silicon nanowires radial core-shell solar cells have recently attracted significant attention as promising candidates for low cost photovoltaic application, benefit from its strong light trapping, and short radial carrier collection distances. In order to establish optics and electricity improvement, a two-dimensional model based on Shockley-Read-Hall recombination modes has been carried out for radial core-shell junction nanowires solar cell combined with guided resonance modes of light absorption. The impact of SiNWs diameter and absorption layer thickness on device electrical performance based on a fixed nanowires height and diameter-over-periodicity were investigated under illumination. The variation in quantum efficiency indicated that the performance is limited by the mismatch between light absorption and carriers’ collection length.

Graphene based GaAs junction solar cell is modeled and investigated by Silvaco TCAD tools. The photovoltaic behaviors have been investigated considering structure and process parameters such as substrate thickness, dependence between graphene work function and transmittance, and n-type doping concentration in GaAs. The results show that the most effective region for photo photogenerated carriers locates very close to the interface under light illumination. Comprehensive technological design for junction yields a significant improvement of power conversion efficiency from 0.772% to 2.218%. These results are in good agreement with the reported experimental work.

The article discusses measurement of the exo-electron currents from alternating current power distribution panel (ACPDP) test panel with or without magnesium oxide (MgO) crystals sprayed on MgO film. An inverse relationship was established between the statistical delay time and exo-electron current from the MgO cathode film. The change of the inverse curve may reportedly be due to an increased discharge success probability by the MgO crystals sprayed.